This invention relates to medical instruments, and in particular to devices for directing puncturing devices toward a desired target inside the body of a patient.
A common problem among sufferers of back pain is prolapsed lumbar intervertebral disc, wherein a portion of the disc between two vertebrae in the lower back prolapses outward and causes pressure on a nerve. In the past, the only successful treatment had been major surgery. Because of the substantial trauma caused by such surgery, however, it was not uncommon for the patient to experience a recovery period of ten to twelve weeks before he could return to his previous employment. Recently a new technique has been developed wherein nucleus material of the prolapsed disc is excised by percutaneous aspiration. The disc nucleus is soft and jelly-like in consistency. It can thus be resected and aspirated by use of a specially designed cannula. The aspiration cannula is inserted into the nucleus of the prolapsed disc with the aid of a guide wire or needle prior to connecting it to the aspirating machine. The major problem, however, is that exacting placement of the needle is crucial to avoid nerve damage.
Since the herniation of the disc most frequently occurs between the fourth and fifth lumbar vertebrae, or between the fifth lumbar and sacral vertebrae, the insertion of the needle is very difficult. Particularly in the latter case, the needle must be inserted not only at an angle to the vertical, but also at an angle relative to the sagittal axis, in order to avoid the protective iliac crest of the sacrum. Preferably the needle is inserted at about eight centimeters away from the midline, on the coronal plane of the prolapsed disc level, at an angle of about 45 degrees. In the past, the needle has been inserted by trial and error, while monitoring its placement by fluoroscopic examination.
The difficulty resulting from this requirement of the compound angle is referred to in Moore, et al, U.S. Pat. No. 4,723,544. The structure disclosed in that patent, however, presents other difficulties relating to structural rigidity and integrity. Another structure intended generally for the same purpose is disclosed in Zanetti, U.S. Pat. No. 4,750,487. Both the Moore and the Zanetti structures provide for the attachment of the apparatus to one side of the operating table. A structure is required which provides more structural rigidity and flexibility in placement of the cannula than either of these structures, and still facilitates the attainment of the required compound angle In addition, a structure is required which can provide guidance to the needle from either side of the patient without requiring the removal and replacement of the structure to change sides.
This invention relates to improvements over the apparatus described above and to solutions to some of the problems raised thereby.